Kate Stewart

Whenever you put one or more time counters on a permanent you control, create a 1/1 white Soldier creature token. Whenever Kate Stewart attacks, you may pay {8}. If you do, attacking creatures get +X/+X until end of turn, where X is the number of time counters among permanents you control.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6o3hbk1codpb1hxoe3u0yg.